Is it possible to make shader with possibility to toggle "double sided" in real time? Or how o simulate it?

If it is impossible to make such shader without "faking" it, then how to fake it?
I'll need to have two main inputs:
- Non-transparent texture
- Fully transparent texture
The main question is how to tell some switch to make texture transparent only where normals are negative? Kinda "If this switch is on and the normal looks away from the camera, use that node tree, and if switch is off, use another one"
I hope my english is good enough so You can understand my question :)
Thank You!